This study aims to demonstrate the capability of simulating the flow induced by the dissociation of neutral molecules in a weakly conductive liquid in a full 3D channel. We investigate numerically the EHD pumping through pure conduction phenomenon in a 3D rectangular channel. It is important to verify if the assumptions allowing us to consider that the flow remains 2D are always valid and in which circumstances some 3D phenomena may occur? Not very surprisingly it is observed that while increasing the electric Reynolds number in increasing the electric potential difference between the two electrodes makes the flow becoming turbulent. In such situation 2D computations are not anymore valid.